This invention relates generally to electrical motors, and more particularly to a digital communications link to control and interrogate a variable speed motor used in air moving systems.
Electronically commutated motors (ECMs) are used in a wide variety of applications because they are more efficient than known standard induction motors. ECMs include the efficiency and speed control advantages of a DC motor and minimize the disadvantages of DC motors, e.g., carbon brush wear, short life span, and noise. In Heating, Ventilation and Air Conditioning (HVAC) systems, as well as, known commercial air distributions systems, ECMs automatically adjust blower speed to meet a wide range of airflow requirements. Known ECMs use microprocessor technology to control fan speed, torque, air flow, and energy consumption.
Conventional blower motors are designed to operate at one speed, however, variable speed ECMs can operate at a wide range of speeds. Variable speed in an ECM is important because blowers need to adjust speed to deliver the airflow needed by the HVAC system.
Known ECMs have various modes of operation, and external control circuits determine an operating point of the ECM. In one mode of operation, Pulse Width Modulation (PWM) signals are transmitted to the electrical interface to control motor speed, motor torque and airflow produced by the motor. The operating point of the ECM is determined by an internal microprocessor control circuit that directly responds to a status of various control input lines.